Department of Neuroscience, Science Commons, University of Lethbridge, 4401 University Drive, Lethbridge, AB T1K 6T5, Canada; Department of Psychiatry, Douglas Hospital Research Centre, McGill University, 6875 Boulevard LaSalle, Verdun, QC H4H 1R3, Canada.
Department of Neuroscience, Science Commons, University of Lethbridge, 4401 University Drive, Lethbridge, AB T1K 6T5, Canada.
Behav Brain Res. 2022 Apr 9;423:113790. doi: 10.1016/j.bbr.2022.113790. Epub 2022 Feb 8.
Evidence from genetic, behavioural, anatomical, and physiological study suggests that the hippocampus functionally differs across its longitudinal (dorsoventral or septotemporal) axis. Although, how to best characterize functional and representational differences in the hippocampus across its long axis remains unclear. While some suggest that the hippocampus can be divided into dorsal and ventral subregions that support distinct cognitive functions, others posit that these regions vary in their granularity of representation, wherein spatial-temporal resolution decreases in the ventral (temporal) direction. Importantly, the cognitive and granular hypotheses also make distinct predictions on cellular recruitment dynamics under conditions when animals perform tasks with qualitatively different cognitive-behavioural demands. One interpretation of the cognitive function account implies that dorsal and ventral cellular recruitment differs depending on relevant behavioural demands, while the granularity account suggests similar recruitment dynamics regardless of the nature of the task performed. Here, we quantified cellular recruitment with the immediate early gene (IEG) Arc across the entire longitudinal CA1 axis in female and male rats performing spatial- and fear-guided memory tasks. Our results show that recruitment is greater in dorsal than ventral CA1 regardless of task or sex, and thus support a granular view of hippocampal function across the long axis. We further discuss how future experiments might determine the relative contributions of cognitive function and granularity of representation to neuronal activity dynamics in hippocampal circuits.
遗传、行为、解剖和生理学研究的证据表明，海马体在其纵轴（背腹或隔颞）上的功能存在差异。尽管如此，如何最好地描述海马体在其长轴上的功能和表示差异仍然不清楚。虽然有人认为海马体可以分为支持不同认知功能的背侧和腹侧亚区，但也有人认为这些区域在其表示的粒度上存在差异，其中空间-时间分辨率在腹侧（颞侧）方向上降低。重要的是，认知和粒度假说也对动物在执行具有不同认知行为需求的任务时的细胞招募动态做出了不同的预测。认知功能解释的一种解释意味着背侧和腹侧细胞的招募取决于相关的行为需求，而粒度解释则表明无论任务的性质如何，招募动态都是相似的。在这里，我们在执行空间和恐惧导向的记忆任务的雌性和雄性大鼠的整个 CA1 纵轴上用即时早期基因（IEG）Arc 量化了细胞招募。我们的结果表明，无论任务或性别如何，CA1 的背侧招募都大于腹侧，因此支持了海马体在长轴上的粒度功能观点。我们进一步讨论了未来的实验如何确定认知功能和表示粒度对海马体电路中神经元活动动态的相对贡献。
